Conventionally, in the body panel of the automobile, holes, which are used for operation and inspection, wiring of wire harnesses and the like, attachment of members and the like, are provided. These holes are generally blocked by a resin hole plug in order to prevent water and the like from entering when they are not in use. Regarding the hole plug, various technologies have been developed for the purpose of placing workability, an improvement of water stop (waterproof) ability, or the like.
For example, the following hole plug is well-known. The hole plug is provided with a blind hole in a center, and also includes an insertion portion wherein locking claws locked in an attachment hole are provided on a whole outer circumference, and a non-insertion portion connected to an upper end of this insertion portion. The insertion portion includes an annular arc-like groove provided on a circumferential border of the non-insertion portion, and in the arc-like groove, dividing wall portions extending along a radial direction disposed in a circumferential direction with a predetermined interval, are provided (see Patent Document 1).
Also, for example, a hole plug comprising a head portion and a leg portion projected from a rear surface of this head portion and inserted into the hole of the plate-like member, is well-known. The leg portion is formed so as to have a tube shape by plural standing plates which are plate-like and respectively stand up from the rear surface of the head portion, and on a base end portion of each standing plate portion, an engaging step portion, which clamps a circumferential border portion of the hole of the plate-like member in cooperation with the head portion, is formed. On the inside of each standing plate portion, a supporting portion, comprising a wave-like plate material controlling flexure to the inward of a radial direction thereof, is provided (see Patent Document 2).                Patent Document 1: Japanese Published Unexamined Patent Application No. S61-59067 (Japan)        Patent Document 2: Japanese Published Unexamined Patent Application No. 2004-162808 (Japan)        